Generally, a communications system provides various multimedia services including a voice service. Recently, the communications system is implemented with a multiple-input multiple-output type so that this multimedia service may be provided with a high quality at high speed. That is, in the communications system, the channel capacity is increased by using a plurality of antennas within restricted frequency resources. Hence, the multimedia service can be provided at high speed.
This communications system is made of a plurality of cells which mutually neighbors. At this time, the communications system includes a plurality of base stations for controlling each cell and a plurality of communications terminals connecting to one among base stations. And, in a unit cell, the base station and the communications terminal can perform the communications for the multimedia service. However, in the above described communications system, there is a problem that an interference between cells is generated in a boundary of the cells. This is because that the communications terminal can receive a signal of a plurality base stations in the boundary of cells. At this time, in the communications terminal, a signal for other communications terminal can be operated as interference. Thus, existing techniques repressing the interference between cells exist. By using a decentralized method, a signal of other base station can be prevented from operating as interference with respect to a communications terminal connected to a specific base station. That is, a corresponding base station can restrict or recommend that a precoding matrix index which can generate interference in the communications terminal is used in other base stations. Accordingly, the generation of interference between cells of the communications terminal can be prevented.